Valve devices are commonly employed components and perform a variety of functions in myriad respirator apparatus and related breathing assistance equipment. Some, for example, merely turn on and off the gas flow from a supply of pressurized breathing gas. Others include multiposition valves which may provide an individual with access to more than one gas supply or access So a single gas supply by more than one person. Examples of valves used in respiratory apparatus may be found in U.S. Pat. Nos. 3,238,943, 4,304,229, 4,841,953 and 5,133,347.
More specifically, U.S. Pat. No. 3,238,943 discloses a breathing system which includes a first face mask and a breathing selector in which the selector has two valve seats to permit passage of air to either the first face mask or to the first face mask and a second face mask, in order to permit breathable air to be accessed by more than one party from the same air supply.
U.S. Pat. No. 4,304,229 discloses an underwater breathing device including a two-way selection valve which permits a diver to selectively employ either an air supply tank or a snorkel for outside air.
U.S. Pat. No. 4,841,953 discloses an auxiliary air supply system for a breathing apparatus in which an auxiliary source of air is selectively accessed by the user and provided to a face piece independent of the normal air supply. The auxiliary air may be provided to the user if the standard breathing apparatus malfunctions.
U.S. Pat. No. 5,133,347 teaches a mouthpiece valve for respiratory equipment which includes a valve disk operable to close the respiratory gas flow connection to the equipment when the equipment is not in use. The mouthpiece valve may be subsequently unlocked by a single hand motion of the user when the breathing equipment is to be used.
While the valve devices suggested by these systems are effective for their intended purposes, they would be of limited practical use in situations where the user of the breathing equipment were unconscious, e.g., a sleeping patient undergoing assisted ventilation treatment for sleep apnea syndrome. Indeed, for the aforementioned valve devices to be properly operated, they require the selective acts of a conscious individual. Manifestly, a sleeping or otherwise unconscious person is incapable of such acts.
When experiencing assisted ventilation treatment, a sleep apnea sufferer typically breathes through an oral, nasal or oral/nasal respiratory mask which respectively covers the wearer's mouth, nose or mouth and nose. The mask inlet opening is connected to one end of an elongated flexible tube, the opposite end of which is connected to a gas flow generator means (e.g., a blower, or the like) for providing a flow of pressurized air. However, none of the presently known breathing assistance systems used for sleep apnea treatment are believed to be equipped with air source bypass systems. Thus, should the air source malfunction or the pressurized air supply be otherwise cut off, the unconscious patient may not have ready access to the ambient atmosphere.
In this regard, much of the time spent wearing a breathing mask during sleep apnea treatment is while the user is asleep. Consequently, even if manually operated valves providing access to the ambient atmosphere in the event of air source failure were available, they would be of no practical use to an unconscious patient. The sole avenue of relief for the patient is to awaken, remove the mask and breathe through his mouth and/or nose.
Non-rebreathing valves (NRVs) constitute another class of known valves designed for particular use with respiratory equipment. Such valves are usually connected proximate to a breathing mask inlet opening and include a respiratory gas inlet, a respiratory gas outlet and a user's expiratory gas exhaust passageway open to the atmosphere. The purpose of such valves is to permit the flow of pressurized respiratory gas to the user upon user inhalation and to prevent the flow of respiratory gas and permit exhaust of the user's expiratory gases upon exhalation. A typical NRV construction includes an inlet surrounded in the interior of the valve housing by a bellows-like, resilient diaphragm which supports an annular valve seat member which is biased by the diaphragm to seat against an internal shoulder of the valve housing. The valve seat member is provided with a central aperture over which is positioned a flapper valve element biased to cover the aperture. The bias of the valve element is minimal. Consequently, the valve element may become displaced from the aperture under the mild flow of pressurized respiratory gas and/or a user's inhalation force whereby the respiratory gas may pass to the user's airway. Upon exhalation, the force of the expiratory gases closes the flapper valve element thereby sealing the aperture while simultaneously displacing the annular valve seat from the housing shoulder against the bias of the diaphragm such that the expiratory gases may escape through the exhaust passageway. This operation is repeated for each of the user's respiratory cycles and functions quite well so long as the pressurized gas source is operational and supplying a flow of respiratory gas.
However, should the supply of respiratory gas be cut off (e.g., the gas conduit becomes kinked), the user would evacuate any breathing gas remaining upstream of the NRV within a few inhalations. Upon total evacuation, gas flow through the aperture would cease and the diaphragm would bias the annular valve seat against the internal valve housing shoulder. At this point in time, the NRV would for practical purposes cease to function. That is, it would be operable only to exhaust the user's expiratory gases. In other words, although the user's exhalation immediately following total evacuation of the breathing gas supply upstream of the NRV would raise the annular valve seat from the housing shoulder against the bias of the diaphragm and thereby enable the expiratory gas to be discharged through the exhaust passageway, that exhalation would necessarily be followed by an inhalation whose force (in combination with the diaphragm bias) would cause the annular valve seat to engage the valve housing shoulder, whereby the user would be cut off from breathing gas of any kind, i.e., either from the pressurized gas source or the ambient atmosphere. At this point, the user would have to remove the mask in order to breathe. In the case of a sleeping user, such as a patient undergoing sleep apnea treatment, the patient would therefore be awakened upon failure of the respiratory gas supply, thereby defeating the central purpose of the treatment, namely, uninterrupted, therapeutic and restful sleep.
The reader will readily appreciate that the detrimental impact upon the patient's sleep patterns (which are intrinsically hindered by the episodic upper airway obstructions associated with sleep apnea) is thus compounded by the additional disturbances attendant to air source malfunctions. More particularly, those afflicted with sleep apnea experience sleep fragmentation and intermittent, complete or nearly complete cessation of ventilation during sleep with potentially severe degrees of oxyhemoglobin unsaturation. These symptoms may be translated clinically into debilitating daytime sleepiness, cardiac dysrhythmias, pulmonary-artery hypertension, congestive heart failure and cognitive dysfunction. Other consequences of sleep apnea include right ventricular dysfunction with cot pulmonale, carbon dioxide retention during wakefulness as well as during sleep, and continuous reduced arterial oxygen tension. In extreme cases, hypersomnolent sleep apnea patients may be at an elevated mortality risk from these factors as well as from accidents while driving and/or operating potentially dangerous equipment. Hence, by eliminating air source obstruction/malfunction problems, sleep apnea treatment may proceed with efficacy, thereby minimizing the damaging effects experienced by sleep apnea sufferers.
Another drawback to known sleep apnea treatment systems is that some patients find the direct facial impingement of the incoming breathing gas flow (as well as other effects of the treatment) to be-so uncomfortable and/or distracting that they cannot tolerate the therapy. As a result, compliance with the treatment by comparatively sensitive patients is somewhat less than the general patient population, whereby those patients are effectively precluded from the therapeutic benefits of the treatment.
An advantage exists, therefore, for a safety valve device adapted for use with respiratory equipment of a type which provides a pressurized flow of breathing gas, which valve device would be self-regulating and pressure-responsive so as to provide access to the ambient atmosphere in the event of malfunction of the respiratory equipment.
A further advantage exists for a diffuser element adapted for positioning in the inlet of the breathing mask which enhances the user's comfort during sleep apnea treatment by diffusing or dispersing the flow of breathing gas as it enters the respiratory mask.